Power generation system based on gas-liquid integrated free plunger expansion machine

Abstract

The invention relates to the technical field of expansion machines and natural gas differential pressure energy utilization, in particular to a power generation system based on a gas-liquid integrated free plunger expansion machine. The power generation system comprises an energy recovery and conversion unit set, a return energy accumulator unit set and a constant-frequency generator set. The energy recovery and conversion unit group comprises a free plunger expansion unit exhaust phase, a free plunger expansion unit expansion phase and a free plunger expansion unit air inlet phase, and the number of the free plunger expansion unit air inlet phase is at least one. The power generation system based on the gas-liquid integrated type free plunger expansion machine can realize that the parallel expansion machine is matched with high flow of a wellhead and the serial expansion machine is matched with high pressure or ultrahigh pressure of the wellhead, and has the advantages of flexible arrangement of the expansion machines, wide working condition adaptation range, high conversion efficiency, high safety and stability, high power generation quality and the like; and implementation and popularization of well mouth natural gas differential pressure energy recovery are facilitated.

Description

Technical Field

[0001] The invention relates to the technical field of expanders and natural gas pressure difference energy utilization, and in particular to a power generation system based on a gas-liquid integrated free plunger expander. Background Art As a clean and environmentally friendly fossil energy, natural gas produces less carbon dioxide when burned than other fossil fuels. When natural gas flows out from the wellhead, due to the high pressure of natural gas at the wellhead, which can usually reach 20MPa or above, the natural gas needs to be throttled and reduced to the pressure range of 6~10MPa that the gas gathering station can handle.

[0003] At present, the main method of reducing the pressure of natural gas from wellhead high-pressure natural gas to gas gathering stations or gathering and transmission pipelines is to use a throttle valve, but this pressure reduction method will waste a lot of energy. Summary of the invention

[0004] The purpose of the present invention is to provide a power generation system based on a gas-liquid integrated free-piston expander to solve the problem that the current method of reducing the pressure of natural gas from the wellhead high-pressure natural gas to the gas gathering station or the gathering and transportation pipeline is mainly to use a throttle valve, but this method of reducing the pressure will waste a lot of energy.

[0005] To achieve the above-mentioned object, the present invention provides a power generation system based on a gas-liquid integrated free plunger expander, the power generation system based on the gas-liquid integrated free plunger expander comprises an energy recovery and conversion unit group, a return accumulator unit group and a constant frequency generator group, the return chamber of the energy recovery and rotation unit group is connected to the return accumulator unit group, and the output end of the energy recovery and rotation unit group is connected to the constant frequency generator group; The energy recovery and conversion unit group includes a free plunger expansion unit exhaust phase, a free plunger expansion unit expansion phase and a free plunger expansion unit intake phase, the number of the free plunger expansion unit intake phase is at least 1, the free plunger expansion unit exhaust phase, the free plunger expansion unit expansion phase and the free plunger expansion unit intake phase are all composed of a gas-liquid integrated free plunger expander, the free plunger expansion unit exhaust phase, the free plunger expansion unit expansion phase and the free plunger expansion unit The number of the gas-liquid integrated free-piston expanders in the intake phase is at least one, each of the gas-liquid integrated free-piston expanders is connected to the high-pressure wellhead natural gas through an intake control valve, each of the gas-liquid integrated free-piston expanders is connected to the low-pressure gathering pipeline through an exhaust control valve, each of the gas-liquid integrated free-piston expanders is connected to the return accumulator unit group through a first one-way valve and an oil pipe, and each of the gas-liquid integrated free-piston expansion mechanisms is connected to the constant frequency generator set through a second one-way valve.

[0006] Among them, when there are multiple gas-liquid integrated free piston expanders set on the exhaust phase of the free piston expansion unit, the expansion phase of the free piston expansion unit and the intake phase of the free piston expansion unit, two adjacent gas-liquid integrated free piston expanders are connected through parallel and series control valves.

[0007] Among them, a high-pressure natural gas inlet and a low-pressure natural gas exhaust port are respectively arranged on both sides of the bottom of each of the gas-liquid integrated free piston expanders, an isolation valve core is arranged in the middle of the top of each of the gas-liquid integrated free piston expanders, and a plunger is arranged inside each of the gas-liquid integrated free piston expanders. The cross-section of the plunger is U-shaped, and an expansion chamber is formed between the plunger and the inner bottom of the gas-liquid integrated free piston expander. The top of the plunger is arranged on the outside of the bottom of the isolation valve core, and a return oil chamber is arranged inside the plunger. The top of the isolation valve core is provided with a return oil chamber inlet and outlet, and an energy recovery chamber is formed between the top of the plunger and the outer wall of the isolation valve core. The energy recovery chamber oil inlet and the energy recovery chamber oil outlet are respectively arranged on both sides of the top of each of the gas-liquid integrated free piston expanders.

[0008] Among them, each of the gas-liquid integrated free-piston expanders has a high-pressure hydraulic sealing ring, a low-pressure gas-liquid sealing ring and a high-pressure gas-pressure sealing ring arranged on the inner wall in sequence from top to bottom, and each of the gas-liquid integrated free-piston expanders has an air leakage chamber and an oil leakage chamber arranged on the inner wall, the air leakage chamber is located between the high-pressure gas-pressure sealing ring and the low-pressure gas-liquid sealing ring, and the oil leakage chamber is located between the low-pressure gas-liquid sealing ring and the high-pressure hydraulic sealing ring.

[0009] Among them, the return accumulator unit group includes an accumulator, a first pressure gauge, a third one-way valve, an oil replenishment pump, a first oil tank and a relief valve. The accumulator is connected to the multiple return oil chamber inlets and outlets through a pipeline, and the first pressure gauge is arranged on the pipeline connecting the accumulator and the multiple return oil chamber inlets and outlets. The accumulator is respectively connected to the first oil tank and the multiple energy recovery chamber oil inlets through pipelines, and the third one-way valve and the oil replenishment pump are arranged in sequence on the pipeline connecting the accumulator and the first oil tank. The first oil tank and the first pressure gauge are connected by a pipeline, and the relief valve is arranged on the pipeline connecting the first oil tank and the first pressure gauge.

[0010] Among them, the constant frequency generator set includes a flow meter, a filter accumulator, a second pressure gauge, a safety valve, a variable motor, a torque sensor, a generator, a synchronizer, a constant frequency alternating current and a second oil tank. Multiple energy recovery chamber oil discharge ports are connected to the second oil tank through pipelines. The flow meter, the filter accumulator, the second pressure gauge and the variable motor are arranged in sequence between the pipelines connecting the multiple energy recovery chamber oil discharge ports and the second oil tank. The second oil tank is connected to the filter accumulator pipeline. The safety valve is arranged on the pipeline connecting the second oil tank and the filter accumulator. The variable motor is connected to the torque sensor and the generator in sequence. The generator outputs constant frequency alternating current through the synchronizer.

[0011] A power generation system based on a gas-liquid integrated free piston expander of the present invention comprises an energy recovery and conversion unit group, a return accumulator unit group and a constant frequency generator group, the energy recovery and conversion unit group comprises an exhaust phase of a free piston expander group, an expansion phase of a free piston expander group and an intake phase of a free piston expander group, the number of the intake phase of the free piston expander group is at least one, the number of the gas-liquid integrated free piston expanders on the exhaust phase of the free piston expander group, the expansion phase of the free piston expander group and the intake phase of the free piston expander group is at least one, due to the setting of the parallel and series control valves, the power generation system based on the gas-liquid integrated free piston expander can realize the matching of parallel expanders with large wellhead flow and series expanders with high or ultra-high wellhead pressure, and has the advantages of flexible expander arrangement, wide adaptability to working conditions, high conversion efficiency, safety and stability and power generation quality, etc., which is conducive to the implementation and promotion of recovery of wellhead natural gas pressure difference energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0013] Figure 1 It is a structural schematic diagram of a power generation system based on a gas-liquid integrated free plunger expander provided by the present invention.

[0014] Figure 2 It is a cross-sectional view of the internal structure of the gas-liquid integrated free plunger expander provided by the present invention.

[0015] 1-free plunger expansion unit exhaust phase, 2-free plunger expansion unit expansion phase, 3-free plunger expansion unit first intake phase, i-free plunger expansion unit second intake phase, 4-accumulator, 5-first pressure gauge, 6-third one-way valve, 7-oil replenishment pump, 8-overflow valve, 9-first oil tank, 10-flow meter, 11-filter accumulator, 12-second pressure gauge, 13-safety valve, 14-variable motor, 15-torque sensor, 16-generator, 17-synchronizer, 18-constant frequency AC, 19-second oil tank, 20-high-pressure natural gas inlet , 21-expansion chamber, 22-low-pressure natural gas exhaust port, 23-plunger, 24-return oil chamber, 25-air leakage chamber, 26-oil leakage chamber, 27-high-pressure gas sealing ring, 28-low-pressure gas-liquid sealing ring, 29-high-pressure hydraulic sealing ring, 30-energy recovery chamber oil inlet, 31-return oil chamber oil inlet and outlet, 32-energy recovery chamber oil discharge port, 33-isolating valve core, 34-energy recovery chamber, 35-gas-liquid integrated free plunger expander, 36-intake control valve, 37-exhaust control valve, 38-first one-way valve, 39-second one-way valve, 40-parallel series control valve. DETAILED DESCRIPTION

[0016] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0017] See also Figure 1 and Figure 2 The present invention provides a power generation system based on a gas-liquid integrated free plunger expander, the power generation system based on the gas-liquid integrated free plunger expander comprises an energy recovery and conversion unit group, a return accumulator unit group and a constant frequency generator group, the return chamber of the energy recovery and rotation unit group is connected to the return accumulator unit group, and the output end of the energy recovery and rotation unit group is connected to the constant frequency generator group; The energy recovery and conversion unit group includes a free plunger expansion unit exhaust phase 1, a free plunger expansion unit expansion phase 2 and a free plunger expansion unit intake phase. The number of the free plunger expansion unit intake phases is at least 1. If the number of the free plunger expansion unit intake phases is multiple, the free plunger expansion unit intake phases include a free plunger expansion unit first intake phase 3 and a free plunger expansion unit second intake phase i (i≥3). The free plunger expansion unit exhaust phase 1, the free plunger expansion unit expansion phase 2 and the free plunger expansion unit intake phase are all composed of a gas-liquid integrated free plunger expander 35. The number of the gas-liquid integrated free plunger expanders 35 on the exhaust phase 1 of the unit, the expansion phase 2 of the free plunger expander unit and the intake phase of the free plunger expander unit is at least 1, each of the gas-liquid integrated free plunger expanders 35 is connected to the high-pressure wellhead natural gas through the intake control valve 36, each of the gas-liquid integrated free plunger expanders 35 is connected to the low-pressure gathering pipeline through the exhaust control valve 37, each of the gas-liquid integrated free plunger expanders 35 is connected to the return accumulator unit group through the first one-way valve 38 and the oil pipe, and each of the gas-liquid integrated free plunger expanders 35 is connected to the constant frequency generator set through the second one-way valve 39; When there are multiple gas-liquid integrated free piston expanders 35 arranged on the exhaust phase 1 of the free piston expansion unit, the expansion phase 2 of the free piston expansion unit and the intake phase of the free piston expansion unit, two adjacent gas-liquid integrated free piston expanders 35 are connected via a parallel-series control valve 40.

[0018] In this embodiment, due to the setting of the parallel and series control valve 40, the power generation system based on the gas-liquid integrated free-piston expander can achieve parallel expander matching wellhead large flow and series expander matching wellhead high pressure or ultra-high pressure, and has the advantages of flexible expander arrangement, wide adaptability to working conditions, high conversion efficiency, safety and stability, and high power generation quality, which is conducive to the implementation and promotion of recovery of wellhead natural gas pressure difference energy.

[0019] Furthermore, the phase difference calculation formula of the free plunger expansion unit exhaust phase 1, the free plunger expansion unit expansion phase 2 and the free plunger expansion unit intake phase is: 360° / i. Since the working cycle of the gas-liquid integrated free plunger expansion machine 35 can be divided into three stages, including the intake stage (such as Figure 1 The free plunger expander unit intake phase), expansion phase (such as Figure 1 The free piston expander in the expansion phase 2) and the exhaust phase (such as Figure 1The free plunger expansion unit exhaust phase 1), so the phase i value should be greater than or equal to 3, and the larger the value of i, the smaller the flow pulsation, and the specific value depends on the wellhead natural gas operating conditions.

[0020] Furthermore, since the working cycle of the gas-liquid integrated free piston expansion machine 35 arranged on the free piston expansion unit exhaust phase 1, the free piston expansion unit expansion phase 2 and the free piston expansion unit intake phase includes an intake stage, an expansion stage and an exhaust stage, the free piston expansion unit exhaust phase 1, the free piston expansion unit expansion phase 2, the free piston expansion unit first intake phase 3 and the free piston expansion unit second intake phase i can all switch between the three stages of exhaust, expansion and intake during actual operation. Therefore, the free piston expansion unit exhaust phase 1 is not limited to the exhaust stage, the free piston expansion unit expansion phase 2 is not limited to the expansion stage, the free piston expansion unit first intake phase 3 and the free piston expansion unit second intake phase i are not limited to the intake stage.

[0021] Furthermore, a high-pressure natural gas inlet 20 and a low-pressure natural gas exhaust 22 are respectively provided on both sides of the bottom of each of the gas-liquid integrated free plunger expanders 35, an isolation valve core 33 is provided in the middle of the top of each of the gas-liquid integrated free plunger expanders 35, a plunger 23 is provided inside each of the gas-liquid integrated free plunger expanders 35, the cross-section of the plunger 23 is U-shaped, an expansion chamber 21 is formed between the plunger 23 and the inner bottom of the gas-liquid integrated free plunger expander 35, the top of the plunger 23 is arranged on the outside of the bottom of the isolation valve core 33, a return oil chamber 24 is provided inside the plunger 23, a return oil chamber inlet and outlet 31 is provided at the top of the isolation valve core 33, an energy recovery chamber 34 is formed between the top of the plunger 23 and the outer wall of the isolation valve core 33, and an energy recovery chamber oil inlet 30 and an energy recovery chamber oil outlet 32 ​​are respectively provided on both sides of the top of each of the gas-liquid integrated free plunger expanders 35.

[0022] In this embodiment, the cross-section of the plunger 23 provided on each of the gas-liquid integrated free-plunger expanders 35 is U-shaped, so the gas-liquid integrated free-plunger expander 35 is compact in structure, resistant to high pressure, resistant to multiphase flow, and has strong anti-pollution energy, and the upper dead point of each of the plungers 23 is not restricted, and free expansion can be performed.

[0023] Specifically, a high-pressure hydraulic sealing ring 29, a low-pressure gas-liquid sealing ring 28 and a high-pressure gas-pressure sealing ring 27 are arranged on the inner wall of each of the gas-liquid integrated free-piston expanders 35 in sequence from top to bottom, and an air leakage chamber 25 and an oil leakage chamber 26 are also arranged on the inner wall of each of the gas-liquid integrated free-piston expanders 35. The air leakage chamber 25 is located between the high-pressure gas-pressure sealing ring 27 and the low-pressure gas-liquid sealing ring 28, and the oil leakage chamber 26 is located between the low-pressure gas-liquid sealing ring 28 and the high-pressure hydraulic sealing ring 29.

[0024] Furthermore, the return accumulator unit group includes an accumulator 4, a first pressure gauge 5, a third one-way valve 6, an oil replenishment pump 7, a first oil tank 9 and an overflow valve 8. The accumulator 4 is connected to the multiple return oil chamber inlet and outlet ports 31 through a pipeline, and the first pressure gauge 5 is arranged on the pipeline connecting the accumulator 4 and the multiple return oil chamber inlet and outlet ports 31. The accumulator 4 is respectively connected to the first oil tank 9 and the multiple energy recovery chamber oil inlets 30 through pipelines, and the third one-way valve 6 and the oil replenishment pump 7 are arranged in sequence on the pipeline connecting the accumulator 4 and the first oil tank 9. The first oil tank 9 and the first pressure gauge 5 are connected by a pipeline, and the overflow valve 8 is arranged on the pipeline connecting the first oil tank 9 and the first pressure gauge 5.

[0025] Furthermore, the constant frequency generator set includes a flow meter 10, a filter accumulator 11, a second pressure gauge 12, a safety valve 13, a variable motor 14, a torque sensor 15, a generator 16, a synchronizer 17, a constant frequency AC power 18 and a second oil tank 19. The multiple energy recovery chamber oil discharge ports 32 are connected to the second oil tank 19 through pipelines. The flow meter 10, the filter accumulator 11, the second pressure gauge 12 and the variable motor 14 are sequentially arranged between the pipelines connecting the multiple energy recovery chamber oil discharge ports 32 and the second oil tank 19. The second oil tank 19 is connected to the filter accumulator 11 through a pipeline. The safety valve 13 is arranged on the pipeline connecting the second oil tank 19 and the filter accumulator 11. The variable motor 14 is sequentially connected to the torque sensor 15 and the generator 16. The generator 16 outputs constant frequency AC power 18 through the synchronizer 17.

[0026] In this embodiment, the variable motor 14 can automatically change the displacement according to the input and output flow to achieve constant speed output, thereby driving the generator 16 to emit constant frequency current; the variable motor 14 is connected to the torque sensor 15 and the generator 16 through a coupling.

[0027] In summary, the working principles of the free plunger expansion unit exhaust phase 1, the free plunger expansion unit expansion phase 2 and the free plunger expansion unit intake phase 3 are as follows: the intake control valve 36 is opened, and the high-pressure wellhead natural gas enters the expansion chamber 21, at which time it will push the plunger 23 to start moving upward; the intake control valve 36 is closed, and the high-pressure wellhead natural gas expands and does work in the expansion chamber 21, continuing to push the plunger 23 to move upward; the exhaust control valve 37 is opened, and under the action of the return pressure oil of the return accumulator unit group, the plunger 23 moves downward, and the low-pressure natural gas in the expansion chamber 21 is discharged into the low-pressure gathering pipeline, and the gas-liquid integrated free plunger expander 35 completes a working cycle; when the plunger 23 moves upward, it is the pressure difference energy recovery stage, and the plunger 23 compresses the hydraulic oil in the energy recovery chamber 34 to drive the variable motor 14 to rotate, thereby driving the generator 16 to generate electricity.

[0028] Among them, since the number of the gas-liquid integrated free-piston expanders 35 on each phase is at least one (determined according to the production and pressure of the wellhead), and when there are multiple gas-liquid integrated free-piston expanders 35 on a phase, two adjacent gas-liquid integrated free-piston expanders 35 are connected by a parallel-series control valve 40, and the parallel and series connection of the expanders on each phase is achieved by switching the parallel-series control valve 40 (the initial position is parallel); the parallel connection of the expanders can match the large flow (i.e., production) of the natural gas wellhead, and the series connection can match the pressure or ultra-high pressure of the natural gas wellhead, realizing multi-stage expansion, preventing ice blockage and excessive temperature drop, resulting in the need to reheat the expanded natural gas before entering the low-pressure gathering and transportation pipeline.

[0029] What is disclosed above is only a preferred embodiment of the present invention, and it certainly cannot be used to limit the scope of rights of the present invention. Ordinary technicians in this field can understand that all or part of the processes of the above embodiment and equivalent changes made according to the claims of the present invention still fall within the scope of the invention.

Claims

1. A power generation system based on a gas-liquid integrated free plunger expander, characterized in that: It includes an energy recovery and conversion unit group, a return energy accumulator unit group and a constant frequency generator group, the return chamber of the energy recovery and rotation unit group is connected to the return energy accumulator unit group, and the output end of the energy recovery and rotation unit group is connected to the constant frequency generator group; The energy recovery and conversion unit group includes a free plunger expansion unit exhaust phase, a free plunger expansion unit expansion phase and a free plunger expansion unit intake phase, the number of the free plunger expansion unit intake phase is at least 1, the free plunger expansion unit exhaust phase, the free plunger expansion unit expansion phase and the free plunger expansion unit intake phase are all composed of a gas-liquid integrated free plunger expander, the free plunger expansion unit exhaust phase, the free plunger expansion unit expansion phase and the free plunger expansion unit The number of the gas-liquid integrated free plunger expanders in the intake phase is at least 1, each of the gas-liquid integrated free plunger expanders is connected to the high-pressure wellhead natural gas through an intake control valve, each of the gas-liquid integrated free plunger expanders is connected to the low-pressure gathering pipeline through an exhaust control valve, each of the gas-liquid integrated free plunger expanders is connected to the return accumulator unit group through a first one-way valve and an oil pipe, and each of the gas-liquid integrated free plunger expansion mechanisms is connected to the constant frequency generator set through a second one-way valve; When there are multiple gas-liquid integrated free piston expanders arranged on the exhaust phase of the free piston expansion unit, the expansion phase of the free piston expansion unit and the intake phase of the free piston expansion unit, two adjacent gas-liquid integrated free piston expanders are connected via parallel-series control valves.

2. The power generation system based on the gas-liquid integrated free plunger expander according to claim 1, characterized in that: A high-pressure natural gas inlet and a low-pressure natural gas exhaust are respectively arranged on both sides of the bottom of each of the gas-liquid integrated free-piston expanders, an isolation valve core is arranged in the middle of the top of each of the gas-liquid integrated free-piston expanders, a plunger is arranged inside each of the gas-liquid integrated free-piston expanders, the cross-section of the plunger is U-shaped, an expansion chamber is formed between the plunger and the inner bottom of the gas-liquid integrated free-piston expander, the top of the plunger is arranged on the outside of the bottom of the isolation valve core, a return oil chamber is arranged inside the plunger, the top of the isolation valve core is arranged with a return oil chamber inlet and outlet, an energy recovery chamber is formed between the top of the plunger and the outer wall of the isolation valve core, and an energy recovery chamber oil inlet and an energy recovery chamber oil outlet are respectively arranged on both sides of the top of each of the gas-liquid integrated free-piston expanders.

3. The power generation system based on the gas-liquid integrated free plunger expander according to claim 2, characterized in that: A high-pressure hydraulic sealing ring, a low-pressure gas-liquid sealing ring and a high-pressure gas-pressure sealing ring are arranged on the inner wall of each of the gas-liquid integrated free-piston expanders in sequence from top to bottom. An air leakage chamber and an oil leakage chamber are also arranged on the inner wall of each of the gas-liquid integrated free-piston expanders. The air leakage chamber is located between the high-pressure gas-pressure sealing ring and the low-pressure gas-liquid sealing ring, and the oil leakage chamber is located between the low-pressure gas-liquid sealing ring and the high-pressure hydraulic sealing ring.

4. The power generation system based on the gas-liquid integrated free plunger expander according to claim 3, characterized in that: The return accumulator unit group includes an accumulator, a first pressure gauge, a third one-way valve, an oil replenishment pump, a first oil tank and an overflow valve. The accumulator is connected to the multiple return oil chamber inlets and outlets through a pipeline, and the first pressure gauge is arranged on the pipeline connecting the accumulator and the multiple return oil chamber inlets and outlets. The accumulator is respectively connected to the first oil tank and the multiple energy recovery chamber oil inlets through pipelines, and the third one-way valve and the oil replenishment pump are arranged in sequence on the pipeline connecting the accumulator and the first oil tank. The first oil tank and the first pressure gauge are connected by a pipeline, and the overflow valve is arranged on the pipeline connecting the first oil tank and the first pressure gauge.

5. The power generation system based on the gas-liquid integrated free plunger expander according to claim 4, characterized in that: The constant frequency generator set includes a flow meter, a filter accumulator, a second pressure gauge, a safety valve, a variable motor, a torque sensor, a generator, a synchronizer, a constant frequency alternating current and a second oil tank. A plurality of the energy recovery chamber oil discharge ports are connected to the second oil tank through a pipeline. The flow meter, the filter accumulator, the second pressure gauge and the variable motor are sequentially arranged between the pipelines connecting the plurality of the energy recovery chamber oil discharge ports and the second oil tank. The second oil tank is connected to the filter accumulator pipeline. The safety valve is arranged on the pipeline connecting the second oil tank and the filter accumulator. The variable motor is sequentially connected to the torque sensor and the generator. The generator outputs constant frequency alternating current through the synchronizer.

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